Methods: Patients aged 18-75 years, with symptomatic asthma despite low-dose ICS (ACQ ≥1.5 at screening/randomisation), diagnosed ≥3 months prior to enrolment and before age 40, non-smokers or ex-smokers (≥1 year with <10 pack-years), were included. All received stable low-dose ICS for ≥4 weeks and had pre-bronchodilator FEV1 ≥60% and ≤90% of predicted and positive reversibility testing. Patients received 2.5 µg or 5 µg tiotropium or placebo once daily via the Respimat® Soft Mist™ Inhaler for 12 weeks in addition to daily low-dose ICS. Rescue medication (salbutamol/albuterol) was allowed throughout. The primary end point, FEV1 peak(0-3h) response (change from baseline) after 12 weeks, will be analysed using a restricted maximum likelihood-based mixed effects model with repeated measures. Secondary end points include trough FEV1 response, FVC peak(0-3h) response, FEV1 (AUC0-3h), FVC (AUC0-3h), ACQ score after 12 weeks, time to first exacerbation and rescue medication use.

Conclusion: This trial provides information on the bronchodilator efficacy and safety of different doses of tiotropium versus placebo as add-on to low-dose ICS in patients with symptomatic mild persistent asthma.